1. Field of the Invention
The present invention is generally concerned with pressure vessels, that is to say vessels adapted to contain at least one fluid under pressure.
They may be either pressure storage vessels or pressure transmitting vessels.
2. Description of the Prior Art
The present invention is more particularly directed to pressure vessels of this kind which comprise within an enclosure which is in practise a rigid material enclosure a separator which divides said enclosure into two variable volume chambers, namely a liquid chamber and a gas chamber, said enclosure further comprising two spaced orifices, namely a liquid orifice and a gas orifice, with which said liquid chamber and said gas chamber respectively communicate, and which have at least transversely disposed relative to said enclosure a wall, referred to hereinafter for convenience as the transverse wall, spaced from each of said orifices and movable within said enclosure.
This separator may, for example, comprise a flexible material bag the opening in which surrounds one of the two orifices, in practise the gas orifice; in this case it is the bottom of this bag which forms what is referred to herein as the transverse wall of the separator.
As an alternative to this, the separator may comprise a piston; in this case it is the piston which forms the transverse wall, the separator itself being reduced to a transverse wall of this kind.
In all cases the separator employed is intended to isolate from each other the two fluids present within the pressure vessel concerned, one of which is a gas and the other of which is a liquid.
However, malfunctions may occur in service leading to some mixing of the two fluids, in particular by penetration of the liquid into the gas chamber.
Where the separator is a bag, for example, the bag may rupture locally or, if the liquid in question is a chemical product and the material of the bag is relatively sensitive to attack by this product, the bag may progressively become permeable resulting in diffusion of the liquid through its wall.
Similarly, if the separator is a piston the seal between the piston and the enclosure within which it slides may become defective.
The resulting defect is usually detected after the event, as a result of the inevitable consequences that arise on its downstream side, in the utilization circuit to which the pressure vessel concerned is connected.
Where, as is often the case, a number of separate pressure vessels jointly serve the same utilization circuit, it is not possible to know, on observing the effective consequences downstream, which of the pressure vessels is faulty, with the result that it is necessary to check all of them systematically.
To alleviate these disadvantages it has already been proposed to fit a pressure vessel of the kind in question with a sensor responsive to the presence of liquid, this sensor being exposed to the atmosphere in the gas chamber of the pressure vessel.
In French Pat. No. 2,422,055, this sensor is incorporated into a tubular plug in the gas orifice.
An arrangement of this kind has proved and may still prove satisfactory.
However, in what is in practise the most usual case with the pressure vessel disposed vertically with its gas orifice at the top, the sensor employed in this way responds only when the gas chamber is totally filled by the liquid, which may already be too late for the utilization circuit concerned.
The result is substantially the same when, as described in U.S. Pat. No. 4,428,401, the sensor installed in a tubular plug in the gas orifice extends to a limited degree from the gas orifice into the gas chamber.
Moreover, in this case the sensor employed, which operates by a capacitive or inductive method, is of relatively large size, especially in terms of its diameter, which may cause technical problems regarding its installation; also, because of the principle employed, it requires a considerable volume of liquid before it can output a significant signal.
A general object of the present invention is an arrangement which has the advantage of detecting a defect resulting in penetration of liquid into the gas chamber much more quickly and which has a much reduced diameter.